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P13 Electromagnetic Waves (Communications (How much they spread, Much much…
P13 Electromagnetic Waves
Electromagnetic Spectrum
The wavelength of visible light ranges from just below 400nm to above 700nm
Electromagnetic waves transfer energy from a source to an absorber
The human eye can only detect visible light
Velocity = Frequency x Wavelength
Radio waves, microwaves, infrared radiation, visible light, ultraviolet waves, x-rays, gamma rays
Light, Infrared, Microwaves and Radio Waves
Microwaves are used to carry satellite TV programmes and mobile phone calls
Radio waves are used for radio and TV broadcasting, radio communications and mobile phone calls
Infrared radiation is used for carrying signals from remote control handsets and inside optical fibres
Mobile phone radiation is microwave radiation and is also radio waves at near-microwave frequencies
White light contains all the colours of the visible spectrum
Different types of electromagnetic radiation are hazardous in different ways
Microwaves and radio waves can heat the internal parts of people's bodies, infrared radiation can cause skin burns
Communications
How much they spread
Much much information they can carry
How far they can travel
Microwaves are used for satellite TV signals
Radio waves of different frequencies are used for different purposes because the wavelength of waves affects:
Further research is needed to evaluate whether or not mobile phones are safe to use
Carrier waves do this by varying their amplitude
Carrier waves are waves that are used to carry information
Optical fibers are very thin transparent fibers that are used to transmit communication signals by light and infrared radiation
Ultraviolet waves, X-rays and Gamma rays
Gamma rays are used to kill harmful bacteria in food, to sterilize surgical equipment, and to kill cancer cells
Ionizing radiation makes uncharged atoms become charged
X-rays are used in hospitals to make X-ray images
X-rays and gamma rays damage living tissue when they pass through it
Ultraviolet waves have a shorter wavelength than visible light and can harm the skin and they eyes
X-rays in Medicine
X-rays are absorbed more by bones and teeth than by soft tissues
X-rays are ionizing radiation and so can damage living tissue when they pass through it
X-rays are used in hospitals
To make images of your internal body parts
To destroy tumours at or near the body surface